Absolutely Necessary:
1. Doors unlock automatically when you turn off the engine.
2. Windows and sunroof close from remote. Can also code to close via ridges on door handles which is fantastic.
3. Trunk close from remote button and interior button.
4. Auto high beams always activated.
5. Turn off that annoying 90 seconds of dinging when a seatbelt is not fastened.
6. Turn off the warning on your GPS screen when you start the car
7. turn off the warning on your rearview camera screen that kind of blocks your view.
8. Tires show temp and psi under vehicle status.

Other things you can do that you might find useful:
1. Turn off ebrake up and speed lockout for DVD video (don't watch movies when driving, it never ends well!)
2. Opening doors will not interrupt auto window up.
3. Highbeams and fog lights can be on at the same time.
4. Sideview cameras can be activated and left on at any speed.
5. You are in a 535 so you can turn on the torque meter for your video screen. (Badass, but I can't do it on my 550!)